Python web.py HTTP/1.1 GET /" -404 Not Found

= I'm learning python with book "Learn python by the hard way" I'm doing the web exercise, but i cant found a concret information.

import web

urls =( '/hello', 'Index')
app = web.application(urls,globals())
render = web.template.render(<mypath>)

class Index(object):

def GET(self):
   return render.hello_form()

def POST(self):
    form  = web.input(name="Nobody", greet="Hello")
    greeting = "%s, %s" %(form.greet, form.name)
    return render.index(greeting = greeting)

then... in my "hello_form"

<form action="/hello" method="POST">
A greeting <input type=text" name="greet">
<br/>
Your Name:  <input type="text" name="name"
<br/>
<input type="submit>
</form>

well, i cant access to the action="/hello".

but i can acces with action="/" well i dont know wich is the reason

Someone could explain me?